Logical control for discretely metering energy to thermal systems incorporating apparatus and methods for simulating time related temperatures

ABSTRACT

The present invention relates to logically controlled unique temperature systems, and it more particularly relates to methods and apparatus for establishing and controlling thermal systems wherein sensing means may anticipate temperature conditions at other points, such as at the work or loads and wherein the controlled heating means are related to the thermal capacity of the system. This arrangement is particularly compatible with unique logical control wherein the temperature signal(s) is converted to a digital pulse train for logical analysis, in turn capable of controlling the heating means by discrete energy bursts. Also, the computer or logical means are capable of sounding an alarm in the event of abnormal conditions or conditions deviating from predetermined patterns.

United States Patent [72] Inventors Frank W. Leitner; 3,012,126 12/1961 Ferguson 219/501 X Bobby B. Childress, both of Charlotte, N.C. 3,069,623 12/1962 Murgio 328/134 X [21] Appl. No. 779,778 3,300,622 1/1967 Swain 219/501 X [22] Filed Nov. 29,1968 3,365,654 1/1968 Johnson 219/501 X [45,] Patented June 22, 1971 Prima ry Examiner-Bernard A. Gllheany Asslgnee gz r i g g Assistant ExaminerF. E. Bell Attorney-Wilfred o. Caldwell [54] LOGICAL CONTROL FOR DISCRETELY M METERING ENERGY T0 THERMAL SYSTEMS IN A PARA S N M D E ig -z ETHO s ABSTRAGT: The present invention relates to logically con- TEMPERATURES trolled unlque temperature systems, and lt more particularly 27 Claims, 36 Drawing Figs relates to methods and apparatus for establlshing and controlling thermal systems whereln senslng means may an- '[52] US. Cl 219/501, ficipate temperature conditions at other points, such as at the 219/497 work or loads and wherein the controlled heating means are [I'llrelated to the thermal capacity of [he ystem, arrange- [50] Fleld (if Search 219/499, men! is particularly compatible with unique logical c nn- 0 wherein the temperature signal(s) is converted to a digital 340/146-2 pulse train for logical analysis, in turn capable of controlling the heating means by discrete energy bursts. Also, the com- [56] References cued puter or logical means are capable of sounding an alann in the UNITED STATES PATENTS event of abnormal conditions or conditions deviating from 2,846,147 8/1958 Keating 236/32 predetermined patterns. 7

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ATTORNEY LOGICAL CONTROL FOR DISCRETELY METERING ENERGY TO THERMAL SYSTEMS INCORPORATING APPARATUS AND METHODS FOR SIMULATING TIME RELATED TEMPERATURES The principles of this invention teach that exact metering of predetermined bursts of energy may provide exact control of thermal inertia or momentum, given a certain amount of information for logical referencing. It has also been determined that substantially precise momentum control may be obtained if sampling is effected at a sufficiently high rate and known or predetermined quantities of heat are applied, when required, but in metered amounts, each insufficient to produce undesired overshoot or departure from a reference temperature (set point). It is understood that the energy bursts may be applied in continuing discrete fashion or trains or any percentage thereof including, for example, 99.6 percent (i.e., odd percentages of full available power input) or down to a percentage equal to that of one predetermined burst (per any unit of time), as called for by the logic.

In other words, the logic sampling electronic control enables the present thermal arrangement to be employed with extreme accuracy in an on/off type control which is compatible with conventional digital computers. Such a computer may be used in different manners, as for example, it may provide the logical determinations for controlling the discrete bursts of energy input or it may simply comprise parallel connected monitoring and alarm circuitry disposed at the work area or located remotely thereof; or it may serve in both capacities. Thus, it may now be appreciated that such a local or remote monitoring or control station may be used for hundreds or thousands of thermal systems by employing conventional high speed scanning techniques.

The present thennal system enables anticipation by virtue of the use or establishment of a secondary or thermal path different from theprimary thermal path of heat flow from the heat source to the load. The secondary path or paths have at least one point in common with the primary path from which thermal parameters such as rate of heat flow and temperature gradient are known or may be determined, relative to the same factors for the primary path.

Therefore, in sucha closed loop system, various arrangements have been developed for providing matching, anticipating, or lagging conditions along the secondary or simulated path for location for sensing means to relate conditions corresponding to those at the load, which may or may not be inaccessible. lnitially, let it be assumed that the thermal time constants are equal from the heating source to the load and from the heating source to the sensing means, then for anticipation, it is only necessary to add heat to the sensing means, such as by a spiral heater wire or current of warm air, in order to permit it to anticipate the temperature momentum at the load, to control the energy input to the heating means, thereby avoiding overshoot. This may be considered for conditions for load or no load. For example, the preheating of the sensing means may be terminated when set temperature is reached; or the preheating may be relieved when the load is applied, thus calling for more temperature from the heating source in the latter case. Thus, various combinations of the principles herein taught may be made to produce the various embodiments hereinafter described in detail.

Basically, it will now be appreciated that the anticipatory function heretofore associated with electronic controls is now built into the thermal system such that standard computers can be used to monitor and/or control these systems with the only requirements being that the computer examine the digital inputs thereto against stored or known references or patterns to detect faults or deviations.

The analog temperature signal is converted to a discrete digital frequency pulse train as close to its source as possible, and this frequency pulse train is compared with a standard or reference frequency to switch a solid state triac or other type triggering control on and off to control the application of power bursts to the heating means. This high resolution frequency comparison circuit can be made to operate in various binary configurations. However, the simplest provides a single AND circuit, wherein iftwo consecutive pulses from the pulse train do not occur within the negative half-cycle of the reference frequency (which has been divided by 4), then the output from the AND gate triggers a one-shot multivibrator to cause the triac to conduct for the predetermined minimum energy burst. Sampling or pulse comparison is effected at a high rate compared to the time for one minimum energy burst, which in itself is only a tiny amount of energy supplied to the heater, but such tiny amounts can be supplied repeatedly to increase the temperature of the heater substantially. However, exact heat control is maintained because of the relatively high rate analog-to-frequency pulse train representing the sensor temperature compared to the time period for a single energy burst.

With the foregoing in mind, the invention will be better appreciated when examined in the light of various type control systems; such as, on the one hand, the on/off type control, and on the other hand, the proportional type control each with its own particular set of advantages, now for the first time realizable in the unique approach herein set forth.

Looking first at the conventional on/off system, it will be appreciated that it is basically a high resolution arrangement relative to load changes, but it can oscillate about this high resolution set point if the thermal capacity of the heating source is high relative to the thermal inertia and momentum of the system as heretofore existed.

Normally, the proportional type control is utilized to obscure the incompatibility between the control and the thermal system. However, under a given set of conditions, this system may accurately maintain set point temperature but in the event of load changes, ambient temperature changes, supply voltage changes, or other such disturbances, they operate to change the set point.

The present invention presents the ultimate in high resolution of on/off type controllers without overshoot because of the anticipatory built-in arrangement and without oscillation about set point temperature by virtue of the unique minimal energy burst technique.

While it will be understood that the thermal system herein disclosed is useful with other type electrical controls, and that the electronic logical control is useful with other type energy systems including thermal systems, nevertheless, the combination thereof permits anticipation and metering which in turn enables application of the invention to situations heretofore inaccessible, and also to conventional situations with attendant unusual advantages. For example, the invention may be applied to heated godets for handling synthetic yarns. In so doing, not only is a much more reliable and inexpensive control obtained, but it should be pointed out that the walls of the godet may be made of much less material, i.e., thinner material, less expensive material with reduced mass and mechanical inertia, with considerably less power required and with versatility of group monitoring and control at minimal expense with optimum reliability.

It may be further appreciated that with the precise digital logic control incorporated in this arrangement, adjustments are unnecessary and the conditions encountered are go or nogo, i.e., nonnal or fault, and of course the speed of operation is far beyond the capacity of man.

With the foregoing in mind, various objects of the invention are as follows:

The provision of apparatus and methods enabling accurate temperature control for even remote or inaccessible sources or loads.

The provision of apparatus and a method employing analog to digital conversion in close proximity to the sensor or source of original analog temperature data to develop precise, reliable, and repeatable signals unaffected by noise or length of transmission path, to remote control, monitor, alarm, or other devices, when conventional digital system noise immunity techniques are used.

The provision of such a system and method capable of full advantage of the early analog to digital conversion where attenuation losses and wave shape disturbances cannot alter the intelligence because it is a frequency train compatible to telemetering, remote, and computer handling techniques.

The provision of such arrangements for extremely highspeed comparison of load temperature to set point temperature with attendant control beyond human supervision and thus beyond human adjustments under normal working conditions.

The provision of such a system and method incorporating logic alarm networks capable of comprehending patterns depicting the energy demands of the thermal system because of the compatibility of logic and discrete energy burst input power.

The provision of such methods and apparatus wherein the pattern monitored may comprise more than a single parameter compared against more than a single reference; and, many groups thereof to determine a single or plural faults or deviations form the normal.

The provision of such arrangements using a single reference for any number of thermal systems regardless of the location from the reference and regardless of the parameters of the thermal system, i.e., temperature control of a stationary cylindrical body, rotating cylindrical body, vessel rectangular or otherwise, liquid, solid, or gas work control. In other words, the logic control need not be aware of what it is controlling.

The provision of such an arrangement wherein conversion from analog to digital signals enables high-level signals permitting the use of ultrahigh-speed scanners and logic controls without detrimental contact resistance and other disadvantages attendant with Iow-level signal scanning.

The provision of such apparatus and methods enabling relatively low-cost logic-type control with absolute accuracy compared to conventional proportional controls with reset fea tures which are relatively incompatible with digital computers.

The provision of such an arrangement wherein logic is incorporated of the type achieving nonadjustable control, i.e., go or no-go, unlike conventional systems requiring adjustment to varying parameters,

The provision of such a system capable of measuring thermal parameters at a rate much faster than the periods of discrete thermal energy bursts, i.e., a unique type of sampling.

The provision of such a system and method for enabling parallel operations of computer techniques from remote sources for analysis and/or control purposes.

The provision of such a system which eliminates any requirement for analog instrumentation which, as is known, is relatively slow and inaccurate.

The provision of such a thermal system providing built-in anticipatory functions for rapid-energy level change without overshoot, particularly during warmup when the energy level is being accelerated from ambient to set level temperature.

The provision ofa system and method enabling thermal control so that the simulated sensor temperature may be selected nearly equal to, equal to, or greater than the work temperature which may also be time related through predetermined or measured parameters enabling the sensor to reach the set point equivalent temperature at any time relative to the load temperature reaching set point.

With the foregoing in mind, the invention will be better understood from a reading of the following detailed description thereof when taken in the light of the accompanying drawings wherein:

FIG. 1 is a block DIAGRAM broadly to illustrate the type control provided by this system and method,

FIG. 2 is an electrical oscillator circuit for converting temperature signals (resistance variation) to pulse frequency trains, i.e., analog to digital converter,

FIG. 2A shows a suitable power source for the stationary or rotating converter of FIG. 2,

FIG. 3 shows a suitable master or reference oscillator for producing a fixed frequency for use in the logic system,

FIG. 4 is provided to illustrate the basic logic circuitry,

FIG. 5 shows in detail the circuitry of one of the 3 identical integrated chips of FIG. 4,

FIG. 6 shows detail of the circuitry of dual of the integrated chips of FIG. 4, two are in the same flat pack,

FIG. 7 is a chart showing the temperature analog frequency pulse train compared to the master oscillator pulse train and master oscillator frequency divided by 4 square wave,

v FIG. 8 is a similar chart to illustrate the condition wherein the sensed temperature is above the set point temperature,

FIG. 9 charts the pulses and wave forms to show the triggering of energy bursts for power input to the heating means,

FIG. I0 is an overall pulse diagram showing operation throughout the control circuitry in general and the logic circuitry in particular,

FIG. I] shows a suitable alarm type circuit for use in this system,

FIG. 12 is a temperature gradient chart of conventional nature,

FIG. 13 is a conventional temperature-time chart showing warmup overshoot,

FIG. 14 illustrates one manner in which the present invention modifies the conventional temperature gradient chart,

FIG. 15 shows a temperature'time chart for the present invention evidencing lack ofovershoot,

FIG. 6 illustrates a conventional type heater-sensor arrangement,

FIG. I7 is a view of one heater-sensor embodiment of the present invention,

FIG. 18 is a different view ofa portion of FIG. 17,

FIG. 19 shows an alternative arrangement for the sensorheater of the present invention,

FIG. 20 shows a dimensioned thermal system patterned after the systems of FIGS. 17 and 18, and wherein predetermined quantities of electrical insulation may be selected to serve as the control for the heat leak path,

FIG. 21 is a chart. of various thermal coefficients for different materials,

FIG. 22 illustrates a conventional point sensing arrangement for a cylinder or godet,

FIG. 23 suggests the elimination of mass from such an arrangement,

FIG. 24 is a perspective view of the invention incorporating intentional heat leak,

FIG. 25 is a temperature chart for selected temperatures obtaining in the structure of FIG. 24,

FIG. 26 shows one embodiment of the invention applied to an extruder,

FIG. 27 is a view in side elevation of the structure of FIG. 26,

FIG. 28 is a temperature chart for the structure of FIGS. 26 and 27,

FIG. 29 is a schematic representation of an automatic thermal system control useful for multiple installations,

FIG. 30 is an end view of an extruder to illustrate internal heat application and control provided by another embodiment of the invention,

FIG. 31 is a view in side section of the structure of FIG. 30,

FIG. 32 is a temperature chart for the structure of FIGS. 30 and 31, and

FIG. 33 depicts a different embodiment of a heater-sensor thermal arrangement particularly suited for internal or external surface heating along a flat, curved, or cylindrical surface.

FIG. 34 is a view partly in end elevation, broken away to show the section of apparatus incorporating a thermal system particularly applicable to heated godets or the like for the textile field, and

FIG. 35 shows the structure of FIG. 34 in cross section.

Referring now to the drawings, and particularly to FIG. 1, it will be seen that the present logical thermal control system is applied to a load or work piece 1, which may comprise solid,

liquid, or gaseous material. The sensing element 2 is shown in proximity to or remotely of work 1, but spaced therefrom along a heat leak or heat dissipating path having a thermal loss control 3.

Sensor 2 may comprise, in its simplest form, a resistance wire, such asnickel, platinum, or the like in which the resistance changes in proportion to the temperature. This analog temperature resistance change or signal is applied to frequency converter 4 to produce a discrete digital output in the form of a pulse frequency train. The frequency converter may be stationary or rotating, but it is preferably in close proximity to sensor 2 in order that the purest signal possible is converted without an opportunity for the introduction of noise or other disturbances.

The digital signal is now applied as a frequency pulse train to logic detector 5 which also receives a master or reference frequency from source 6. Depending upon which frequency is highest, energy is either applied or-not applied from power source 7 to heater 8 because the logic output over lead 9 serves to trigger the power source 7 for at least one predetermined burst of energy when required. At this point it should be appreciated that comparison of the two input frequencies to logic detector 5 is taking place many times during the intcrval of the minimum predetermined energy burst, such that if further power is required, the logic detector will be instantly ready to trigger in a second, third, or fourth burst of energy until the frequencies are changed so that no further energy is required at that time. However, the logic detector continues to make hundreds or even thousands of comparisons a second, thereby achieving the steady set point temperature without the many disadvantages of the undulating surface temperatures that would be established by a conventional on-off control without such high resolution and without the described metered bursts of power. That is, the logic commits only an incremental, i.e., small or tiny burst of energy and may stop at one burst. This small burst of energy may be so small as to be hardly recognized in the resultant temperature increase that occurs at the work as a result thereof.

Referring to FIG. 1 again, an analog alarm circuit is shown at 10. This alarm circuit is further described in detail in connection with FIG. 11

Obviously, a computer may replace the logic detector 5 and master oscillator 6, as well as alarm 10. Alternatively, it may be connected in parallel with one or all of these components to serve for standby use in the event of malfunction.

FIG. 2 depicts circuitry which is used to convert the sensing resistance '11 to a digital pulse train (block 2 of FIG. I). The power for the oscillator of FIG. 2 is introduced through winding L3 secondary if the oscillator is stationary or rotating, or alternatively through slip rings A and B if the oscillator is rotating. When supplied via L3 rotating kHz. air coil is used. The pulse train output is derived at points C and D if the oscillator is stationary and at points E and F if the oscillator is rotating. The analog to digital oscillator-type converter develops the precise pulse frequency output train in which the repetition rate is controlled by the temperature caused resistance variation of resistor 11 which serves as sensor 2 in FIG. 1.

In FIG. 2 the full wave rectifier bridge 12 is supplied with 24 volts AC which is rectified and filtered by capacitor 13 and resistor 14, with zener diodes l5 and 16 serving to stabilize the DC input to the oscillator portion next to be described.

Generally, the resistance change of sensor bulb 11 causes the voltage at O2 emitter 17 to shift negative in proportion to the resistance change. 01 is a constant current type generator and this constant current charges C1, shown as capacitor 18, at a constant rate. Therefore, the time varying voltage at capacitor 18 or the Q3 emitter is quite linear with times.

O2 is preferrably a transistor of the same type 01 and its temperature sensitive base to emitter voltage varies at the same rate as Q1. These transistors track within 30;]. per degree Centigrade. The ratio of R1 and R2 is chosen to obtain nearly equal emitter currents at the center of the ambient temperaturc range, and Cl is a temperature stable poly carbonate film capacitor with negligible drift to 65C.

O3 is a unijunction transistor and is extremely stable as a level sensing device to produce a high level output pulse when the emitter voltage exceeds this constant level. Cl is discharged via a negative resistance emitter to its lower base path to precise valley voltage where the emitter base junction reverts to a reverse biased diode. C1 recharges linearly to the precise peak point voltage and the cycle repeats with the result being the pulse train output at 03 base whose frequency is a precise analog of the bulb resistance and hence the bulb or godet temperature. The air core coaxial coils L1 and L2, used for rotating oscillators, have a l-to-2 -turns ratio of number 32 wire with L2 preferably having 50 turns and being the stationary coil.

The L2 output pulse train may be utilized, for example, to trigger a monostable multivibrator to produce a constant amplitude constant width rectangular output pulse for each trigger. The result is a DC output voltage which may appear on a conventional indicator or recorder and may be calibrated to read in Centigrade or Fahrenheit degrees.

The nonlinearity of the nickel bulb tends to compensate for the nonlinearity of circuit, resulting in the linear output. Nickel is nonlinear from about 0 to 380 C. lfa platinum bulb is substituted, it must be compensated for electrical nonlinearity, and if a thermistor were to replace the sensing resistor, the sense of the circuit will be reversed and while the sensitivity is increased, the calibration would be less linear.

A silicon diode added between Q3Bl and L1 provides 0.4 to 0.6 volts isolation between stray pick up to L1 and the potential at Q3Bl. This minimizes pickup volts which might incorrectly modulate the Cl voltage and cause erroneous frequency modulation.

In FIG. 2A there is shown a suitable power supply for the oscillator of FIG. 2. Fullwave bridge 20 is supplied with input AC power which is rectified and stabilized by Q8 and O9 to be delivered at winding or coil L, for coupling into L' of FIG. 2.

If L, is a stationary coil, it can induce power into coil L' when the latter rotates. Otherwise the tow coils may comprise stationary transformer windings. Alternatively, the output of the power supply of FIG. 2A may be delivered directly to slip rings A and B of FIG. 2 in the absence of coils L. and L' while still accommodating a rotating oscillator.

In FIG. 3 there is illustrated the master or reference oscillator capable of providing a standard or fixed frequency in the form of a square wave output of one-quarter the frequency of the master oscillator for use in the logical control network. This is a resistance controlled oscillator electrically matched to the oscillator of FIG. 2. However, the calibrated variable resistor 25 (which serves as the group adjustable potentiometer for multiple control) is substituted for the sensing resistor 11 of FIG. 2 to fix the frequency of the reference oscillator. Since this oscillator will always be stationary and usually will serve for multiple thermal systems, as at the computer or in the control room, the input power may be applied as an AC voltage at terminals 26 and 27 of fullwave rectifier bridge 28. Large filtering capacitor 29 is provided for the output from bridge 28. Zener diode 30 and transistors 31 and 32 are provided to regulate and stabilize the voltage for this reference oscillator with 8+ being established at 10 volts on lead 33. Otherwise the oscillating portion of the oscillator of FIG. 3 is identical to the equivalent portion heretofore described in connection with FIG. 2.

The output pulse frequency train from the master oscillator of FIG. 3 is inverted in integrated chip 35 which is a hex invener, manufactured by Motorola and identified as type MC789P. The negative output pulses from chip 35 drive or serve as the clock input to a conventional digital logic .I.K. flip-flop, shown as the integrated chip 36, available as Motorola type MC776P (see FIG. 6). The flip-flop toggles each clock pulse, providing a perfectly symmetrical square wave output at one-half the pulse frequency. A second flip-flop in chip 36 is cascaded with the first flip-flop to produce a divided by 4 square wave. This wave drives an inverting transistor in chip 35 which in turn supplies the master oscillator reference buss 37 with the square reference frequency introduced to the logic circuit of FIG. 4 at lead 37.

The circuitry of the present invention is conveniently deployed on various cards or plug-in plates, facilitating ready assembly, servicing, or replacement. Thus, the master oscillator of FIG. 3 is connected into the logic of FIG. 4, as is also the temperature sensitive oscillator of FIG. 2.

In the control card of FIG. 4, the reference square wave 40 on lead 37 has negative leading edges such as 41 adapted to clock a preset .I.K. flip-flop in chip 42 (shown in detail in FIG. 5) and also to supply one input to diode 43 which, together with diode 44, comprises an AND gate.

The A flip-flop in its preset condition has a Q output of -lor in digital nomenclature, I. This 1 is connected to the preset terminal of a second flip-flop B (chip 48 of FIG. 6 using onehalf of the circuitry thereof) and forces it to remain preset so long as Q of A is 1. Under these conditions B will not respond to other inputs.

As the master oscillator square wave at A swings to from of A swings to O. This enables B to count negative going pulses.

The temperature analog pulse train 45 on lead 46 is inverted in inverter 47 and appears as a negative pulse train at B On the first negative pulse into B Q of B swings to I. On the second negative pulse, 0 swings to O. Q of B is capacitively coupled to the preset terminal (9') 2f flip-flop A via C Therefore, at the second pulse into 8,, Q, swings to l and differentiated positive pulse forces A to preset. (Due to capacitive coupling, A is not held in preset). As A is preset, however, it forces B to preset until the next negative going excursion of the master square wave. The sequence than repeats as follows:

Master oscillator wave form 40 goes to 0, sets A, unlatches B. B counts and at 2, B pulses. A to preset latching Brepeat sequence at next master oscillator negative pulse, etc.

Remembering that the master oscillator wave form drives one input to the AND gate while 0 of B is the second input over leads 49 and 50 (to diode 44) and to obtain a plus output, both inputs must be 1 simultaneously, then it follows that if the count of two by flip-flop B occurs within the negative half-wave of the master oscillator, no output from the AND gate can occur. However, if the count of 2 takes place after the master oscillator pulse swings plus l then a positive output will occur at the AND gate output.

The resulting output pulse varies in pulse width and repetition as a function of the phase and frequency difference between these two nonsynchronous frequencies. The output disappears abruptly as the input pulse train frequency becomes less than the master oscillator pulse train (or less than 4 times the master oscillator square wave frequency).

The result is a high resolution frequency comparison circuit.

The varying pulse width output is detected by allowing it to trigger a one shot multivibrator made up of transistors 51 and 52 and the flip-flop C chip 53 (which is the other one-half of FIG. 6. The plus output pulse from the AND circuit is inverted in inverter 54 (diode 55 serving to hold the voltage to a safe level) and toggles the .I.K. flip-flop C.

Once tripped, it cannot be clocked by virtue of its connection from terminal 9 to until C is preset via the timing circuit. The timing circuit is made up ofa 4.7 microfarad capacitor 56 and a l000,000 ohm resistor 57 plus transistor switch emitterfollower 52 and diode 58.

Terminal 8 ofC chip 53 swings negative when C is toggled. This releases the capacitor 56 to be charged via the 100,000 ohm resistor 57. At a capacitor voltage high enough to equal the drop of the emitter-followerjunction plus the series silicon diode plus preset voltage required at C10, the flip-flop presets. The purpose of the diode 58 is to require about 0.6 volts higher trip voltage to lengthen the duration.

For each plus output of the AND gate (diodes 43, 44), positive pulse of about 0.l second duration appears at terminal 9 of chip 53. This plus pulse biases the blocking oscillator, comprising transistor 60 and associated conventional components, on for a 0.1 second burst of about 2,000 Hertz trigger pulses for a conventional triac (not shown) but having connections M-N thereto. The triac is gated on and applies full 60 Hertz power to the heater (e.g. 8 of FIG. 1) for 0.1 second each time the AND gate shows coincidence.

When the godet (sensed temperature) frequency is low, the 0.l second pulses appear end to end, practically speaking. The time between pulses is in the order of 0.001 second. As the set point is approached, the beat slows down so that pulses may occur with long intervals between.

Each pulse applies a tiny burst of power 0.1 second duration to the heater. The loop is self-adjusting to regulate the godet temperature holding the measured frequencies close to the master oscillator. When the transducer frequency (godet temperature analog) is equal to or greater than the master oscillator frequency, the power is shut off.

The foregoing will now further be explained using the wave form charts of FIGS. 7 through 10 to illustrate a few of the infinite combinations of wave trains that occur in the A, B, and C flip-flops of FIG. 4. FIG. 7 shows precise synchronization of frequency and phase between pulse train 45 and square wave 40, which by nature will occur only for microseconds or less. FIG. 8 shows complete power cutoff at over temperature (frequency of 45 is high relative to 40) since the counter of chip 48 (FIG. 4) will always reset before the plus master oscillator divided by 4 pulse arrives.

FIG. 9 shows a typical instant at a time when the temperature and frequency of 45 is low relative to 40, thereby providing AND gate (from diodes 43, 44, of FIG. 4) output pulses 62, 63 with pulse 62 triggering the one shot multivibrator 51, 52 and C to operative condition at 64.

FIG. 10 shows a typical instant in time relation between the wave forms and the one shot multivibrator. NOTE the OFF time becomes very great and random as set temperature is approached, and at temperature it shuts off completely, when the analog frequency exceeds the master oscillator.

The off temperature alarm circuit of FIG. ll takes advantage of the fact that the 0 terminal 49 (FIG. 4) of flip-flop B has a rectangular pulse 65 (FIG. 10) whose on to off time ratio is a function only of the relative frequencies.

0 of B flip-flop is at zero in the preset condition and B is forced to preset by flip-flop A until the negative edge of the master oscillator square wave 40 toggles A causing its 62 to go v to 0. Call this time T, (FIG. 10).

The first analog pulse 45' following T will toggle B causing 0 to flip to l. The second analog pulse 45" following T will toggle B letting 0 fall to zero.

Simultaneously Q of B goes to I and by its AC coupling to flip-flop A preset terminal, flip-flop A is preset. Flip-flop B has already been toggled to the condition it naturally is forced to by A (no action takes place between A and B until the next master oscillator square wave toggles A, etc.)

Also, in FIG. 10 the time shown as X varies with phase between the two pulse trains. It varies from 0 to 360 where it drops to zero or vice versa. However, the waveform at Q of B stands alone and its duty cycle is precisely a function of the frequency ratios.

Consequently, the average DC is extracted by using this wave form to drive a current generator transistor 67 (FIG ll) to a fixed current level each pulse, by way of inverters 98 and 99 in lead 101.

The constant current pulse at the collector is integrated by a 22 microfarad capacitor 68. This DC is applied to a fixed bias differential amplifier comprising transistors 69 and 70 which is biased for equal current in each collector at 0.25 duty cycle (temperature on set point).

Under these conditions equal voltages of about 330 millivolts, due to the collector to the collector currents, flow in the 1K resistors 7I and 72. These resistors are connected to the gates of small silicon controlled rectifiers (SCR) 73 and 74 which "fire" at 0.5 to 0.6 volts.

A second current from 200,000 ohm potentiometer 75 and a 10,000 ohm series resistor 76 is summed with the collector current. When the two currents cause a voltage drop equal to the SCR firing potential, it fires and latches on to light a series alarm lamp, such as 77 which can be remotely located and such a lamp can be provided for each thermal system or two such lamps could be provided for low or high alarm.

As the duty cycle shifts from 0.25 at the base of transistor 67 due to the frequencies being different, the collector currents of transistors 69 and 70 rise and fall in opposition, and at a frequency sufficiently off temperature, the (appropriate) lamp will light showing the temperature has shifted out of tolerance.

Since the set point is a function of frequency ratio, as other temperatures are programmed by the master control, this alarm set point is inherentlyand automatically-adjusted. That is, it is independent of the absolute frequencies and returns to balance when the ratios are proper.

In the thermal arrangements explained in connection with FIGS. 17 and the FIGS. thereafter, consider first a conventional pin or drum heater adapted to be heated to a controlled temperature for drawing or otherwise handling synthetic yarn. Basically, the designer may select from three heating arrangements, the first employing induction heating; the second, flame or other nonelectrical heating; and the third heating wire disposed within the cylinder.

The object herein is to maximize the sensor heater efficiencies and provide new advantages by taking advantage of as many parameters as possible, such as materials, dimensions, physical deployment, and, in addition simulated arrangements particularly provided for use where the heating surface or work is inaccessible, although this technique may be employed under all circumstances to advantage.

Conventional temperature sensing may be achieved externally using the pyrometer or a thermistor of other sensing unit embedded in the wall of the cylinder. First of all, the temperature gradient obtaining in such an apparatus would show the temperature of the heater higher than the temperature of the sensor, because of the thermal drop from heater, part way through the wall to the sensor, and then, of course, the temperature of the load at the lowest temperature of all because the load or external surface of the drum is more remote from the heater source (see FIG. 12).

The load line or gradient is illustrated at 201. The usual difference in temperature between T' (heater) and T, (load) is large, so it is not only an inefficient arrangement, but also indicates that a good deal of thermal inertia might be encountered in such a system and, inherently it would be subject to slow response, high mass, and an overshoot type arrangement, which when employed with on-off type heat, would also show a substantial unstable set temperature, as may be seen in FIG. 12. Note that the temperature-time curve 203 is relatively slow rising, evidencing the temperature momentum due to the mass. It also substantially overshoots the set temperature as shown at 203'. Additionally, the ripple factor occasioned by the undulations about the set temperature is relatively high.

In FIG. 14, there is shown an idealized gradient wherein the slope of the load line 205 is near zero.

In FIG. 15, there is shown a somewhat idealized temperature-time curve 207 wherein no overshoot is present and the ripple factor is an absolute minimum for an on-off type control. Additionally, the rise time of curve 207 to set point temperature is much less and overshoot has been completely eliminated. The sensor-heater arrangement herein described produces the gradient and response curves approximating FIGS. 14 and 15. In actual practice, gradient 209 in FIG. 14 is obtainable, whereas the response curve 207 of FIG. 15 is an obtainable companion curve therefore. Moreover, the invention provides unusual control over the gradient, as for example, the gradient 210 of FIG. 14 may be produced or various other unique gradients.

In FIG. 16 there is shown conventional type approach to a heater-sensor arrangement wherein the drum or cylinder section 211 is shown with an internal heater 212, a sensor 213, and a load in the form of synthetic strands 214. It can be seen that heat is lost by internal radiation 215 and external radiation 217. Obviously, the metal 211 accounts for a large thermal drop and additionally, it may be noted that the point sensor 213 ordinarily embedded in metal 211 via an edge hole or aperture is not symmetrical thermally with the load or heater; and, of course, is at a substantially different temperature than either.

With the conventional heater and control in mind, the principles obtaining in the novel arrangements hereinafter depicted will first be discussed followed by a description of the structure preferred in the embodiments to appear hereinafter. Therefore, looking at FIGS. 17 and 18, it will be seen that the basic thermal conductivity equation:

rm= =l Q/ 1 U may be applied to the heated body 211', which has dimensions of a thickness corresponding to L, a width corresponding to W and a height corresponding to H. The temperatures are T which is the temperature of the inside surface with T, being the temperature of the working surface. The total energy dis sipated over the working surface having an area of W times H is identified as Q. The, for a given heat flow per unit of area, the temperature gradient dclta T is equal to T minus T,,,,,. The basic equation covering the relationship herein described, as above set forth, is delta T equals Q over A (times L over K) where K is the thermal conductively of the solid, the other parameters or quantities having previously been defined.

Looking at this equation, it appears obvious that for a given material (K), the temperature gradient is directly proportional to the thickness (L), and it is desired in the embodiment hereinafter set forth to decrease the gradient and, therefore, the thickness or L dimension is made as small as feasible, for example, 40 to 50 percent of the thickness of the conventional body such as 211 in FIG. 16.

The other quantities of this equation will be analyzed in detail to provide guidelines for the design of the new embodiments, but in the meantime, the object is to produce a structure capable of creating a temperature approximating T without access to this temperature or surface, through simulation by intentionally establishing and using a heat leak which dissipates a small percentage of total energy or heat in the primary load or work path in the form of a second gradient with known parameters and conditions for normal operation to permit sampling or control through computer logic, based on this simulated gradient.

Interestingly enough, now that there is recognized a primary and secondary path, these may be interrelated by selecting a common temperature point, such as the temperature of the inside surface of the body to be heated, and build therefrom indifferent dircctions, the primary gradient to the load and the intentional heat leak gradient or secondary gradient, through the simulated path to obtain the necessary information without access to the load itself or surfaces attendant thereto. Thus, heat flow can be controlled before and after the sensor-in this case, a space sensor.

Next, the dimension of time as a parameter will be brought into the study to indicate that the materials selected may control this parameter and hence, influence the gradient in an unusual or different way.

Looking to the table of FIG. 21, it will be appreciated that the various characteristics for three metals, aluminum, steel, and brass are compared as to their thermal qualities. Considering first aluminum, there will be noted that its thermal conductivity, which relates directly to the gradient, measures I540 B.t.u. per square foot per degree Fahrenheit for 1 inch thickness. Whereas, steel has a measure of 360. Thus, a greater temperature differential, almost 4 to 1 will appear across the same thickness of aluminum as steel. However, I

when the columns for specific heat and specific gravity are multiplied together to take into account the inherent properties and densities relative to thermal capacities of these metals, it will be appreciated that the measure of time from a 

1. An electronic logic control apparatus for providing a timed output signal when one frequency signal is different in a predetermined direction from a fixed frequency signal comprising, means for developing the fixed frequency signal as a square wave train at a fraction of the original fixed frequency; AND gate means connected to receive as one input thereof the square wave train; means for developing said one frequency signal variable in frequency in proportion to an energy level means for determining if a selected number of pulses of said one frequency signal occur during a selected portion of the square wave train to produce one condition at the AND gate means by applying a pulse as another input to the AND gate means; and means responsive to the AND gate means during said condition to produce said timed output signal metered over a predetermined time interval.
 2. The control apparatus of claim 1 wherein the means for developing the fixed frequency signal comprise oscillator means for developing the fixed frequency signal; and means for dividing the frequency and converting the signal to a square wave train
 3. The control apparatus of claim 1 wherein the means for determining if a selected number of pulses of said one frequency occur during a selected portion of the square wave train comprises counting and gating means operable by said one frequency signal and the square wave train.
 4. The control apparatus of claim 3 wherein the counting and gating means applies output pulse to the AND gate means upon detection of said condition; the other signal to said AND gate means comprising the square wave train.
 5. The control apparatus of claim 1 wherein the means responsive to the AND gate means comprises multivibrator means triggered by the AND gate means upon detection of said condition.
 6. The control apparatus of claim 1 further comprising alarm means operable from the means for determining if a selected number of pulses in response to a frequency deviation of a predetermined amount between said one frequency and the fixed frequency. 7 The control apparatus of claim 1 further comprising means for developing said one frequency signal be sensing said energy level directly.
 8. The control apparatus of claim 1 further comprising means for developing said one frequency signal by sensing said energy level indirectly.
 9. The control apparatus of claim 1 further comprising means responsive to variations of said energy level to produce an analog signal indicative thereof, and means for converting the analog signal to a digital frequency pulse train to comprise said one frequency signal.
 10. The control apparatus of claim 1 further comprising heating means for at least one thermal load; and heat sensing means for developing said one frequency signal in accordance with the heat energy level sensed.
 11. The control apparatus of claim 10 further comprising means for supplying energy to the heating means in response to said timed output signal.
 12. The control apparatus of claim 10 further comprising means for supplying energy to the heating means; control means for said means for supplying responsive to said timed output signal to cause the means for supplying to supply metered energy bursts to the heating means corresponding in time to the period of each timed output signal.
 13. The control apparatus of claim 1 for controlling a thermal system further comprising a primary heat flow path from a heat source to a load; a secondary heat flow path extending from the primary heat flow path; sensing means responsive to said energy level of heat in the secondary path at a given position to develop said one frequency signal; heat flow control means in the secondary heat flow path between the primary heat flow path and the given position to simulate load conditions at the sensing means; and means for adjusting the magnitude of heat flow along the primary path in response to said timed output signal.
 14. A electronic logic control apparatus for providing a metered output when one frequency is different from another frequency comprising, means for developing a fixed frequency; means for converting the fixed frequency to a square wave train at a fraction of the original fixed frequency; AND gate means connected to receive as one input thereof the square wave train and as the otherinput thereof a conditional signal in accordance with the other frequency; means for determining if a selected number of the other frequency pulses occur during a selected portion of the square wave to produce said conditional signal at the AND circuit to cause an output therefrom; and means responsive to said output therefrom at the AND circuit for metering for a predetermined time interval.
 15. Logical thermal control apparatus comprising in combination means for supplying heat to a load; control means for the heat supply means; temperature sensing means disposed relative to the load to simulate the temperature thereof; means for converting the sensed temperature to a digital frequency pulse train; logic means; means for supplying the digital frequency pulse train to the logic means; means for supplying a fixed frequency to the logic means for a determination of whether the load temperature is below, equal to, or above a predetermined temperature and producing a signal when the load temperature is below the predetermined temperature; and means for energizing the control means for a predetermined amount of energy to be supplied to the heating means in response to said signal.
 16. The control apparatus of claim 15 wherein the temperature sensing means comprise thermal control means disposed to receive a portion of the supplied heat and having thermal coefficeints to modify the flow of said portion to simulate load conditions.
 17. A multiload temperature control system comprising a plurality of heating means respectively associated with the loads for bringing load temperatures to predetermined set point temperatures through on-off power bursts; a plurality of temperature sensors respectively disposed in heat dissipating paths of the loads; resistance to frequency converters respectively in electrical connection with each of the temperature sensors and physically deployed in proximity thereto to develop frequency pulse trains indicative of the temperatures being sensed; means for developing a reference frequency and for logically comparing the frequency pulse trains and the reference frequency to produce control signals for the load heating means associated with the loads at temperatures less than set point; and means sequentially introducing said frequency pulse trains to the means for developing and comparing and for sequentially applying said control signals to the heating means.
 18. The control system of claim 17 wherein the load heating means meter input power in predetermined energy bursts to heat the load in response to said control signals, and said control signals being of relatively short time duration relative to the time interval of a predetermined energy burst whereby the multiload temperature control is effected from a single means for developing and comparing.
 19. Apparatus for providing timed output signals when the frequency of a first signal changes in a predetermined direction and amount as determined relative to a fixed frequency periodic timing wave, comprising in combination means for developing said periodic timing wave; coincident detector means connected to receive as one input thereof said timing wave and as another input thereof a logical control signal; counting means responsive to the frequency of said first signal and the timing wave to develop said logical control signal when the frequency of said first signal varies said amount in the predetermined direction; and meanS responsive to the occurrence of said logical control signal to produce the timed output signal over a predetermined period of time.
 20. Apparatus in accordance with claim 19 further comprising means responsive to variations of an energy level to produce an analog signal indicative thereof; and means for converting the analog signal to a digital frequency pulse train to comprise said first signal.
 21. Apparatus in accordance with claim 20 further comprising heating means for a thermal load, means for supplying energy to the heating means; and control means for the means for supplying responsive to said timed output signal.
 22. A method of maintaining a predetermined set temperature at an electrically heated load comprising the steps of: deriving an analog temperature signal in accordance with the instantaneous temperature of the load; converting said analog temperature signal to a digital pulse train having a frequency in accordance with the temperature; deriving a fixed frequency periodic timing wave; counting the occurrence of signal frequency manifestations relative to the time of occurrence of selected waves of the periodic timing wave; establishing an electrical heating path to the load whenever a predetermined count is realized; and introducing a discrete amount of heating current each time said predetermined count is sensed.
 23. A method of controlling the temperature of a load using on-off heating control comprising the steps of: determining a minimum predetermined energy burst relative to the load which will change its temperature almost undetectably; sensing the temperature of the load relative to a predetermined temperature; applying a minimum predetermined energy burst to the load when the sensed temperature is below the predetermined set temperature; and sensing the load temperature one or more times during the time interval of the application of the minimum predetermined energy burst in order that a commitment of successive minimum predetermined energy bursts may be determined if required to permit the application of almost continuous energy to the load until set temperature is attained.
 24. The method of controlling the temperatures of a plurality of loads in accordance with claim 23 by the further step of sequentially scanning the temperature signals from the plurality of loads respectively at a rate sufficiently high to scan all temperature signals at least one during the period of a minimum predetermined energy burst.
 25. On-off type logical thermal control apparatus comprising in combination means for supplying heat to a load; control means for the heat supply means; temperature sensing means disposed relative to the lead to simulate the temperature thereof; means for converting the sensed temperature to a digital frequency pulse train; logic means; means for supplying a digital reference to the logic means for a determination of whether the load temperature is below, equal to, or above a predetermined temperature and producing a signal when the load temperature is below the predetermined temperature; said control means comprising means for metering energy into predetermined amounts measured over predetermined periods of time in which each predetermined amount is sufficient only to urge the load temperature upwardly; and means for energizing the control means for a predetermined amount of energy to be supplied to the heating means in response to said signal the temperature sensing and conversion being accomplished at a rate equal to at least once during the time of a predetermined time interval.
 26. A method of supplying thermal energy to a load through application of heat in on-off fashion comprising the steps of: establishing a reference indicative of a set temperature for the load; instantaneously sensing temperature indicative of the load temperature; converting the sensed temperature to a temperature indicative signal; logically comparing the reference indicative of the set temperature with the sensed indicative temperature signaL to determine if the load temperature is below set temperature; applying a predetermined amount of energy to the load metered over a predetermined time interval when the load temperature is below set temperature and which amount is sufficient only to elevate minutely the load temperature; continuing the instantaneous sensing and logical comparison to continue the application of predetermined amounts of energy until the load reaches set temperature; said instantaneous sensing being accomplished at a rate equal to at least once during each time interval corresponding to said predetermined time interval.
 27. Apparatus for controlling the application of thermal energy to a load in on-off fashion comprising, in combination means establishing a reference indicative of set temperature for the load; means instantaneously sensing temperature indicative of the load temperature; means for converting the sensed temperature to a temperature indicative signal; means responsive to the reference indicative of set temperature and the temperature indicative signal for logically comparing them to determine if the load temperature is below set temperature; means for metering a predetermined amount of energy over a predetermined time interval which amount is sufficient only to elevate the load temperature minutely; and means for applying energy in predetermined amounts to the load as long as the load temperature is below set temperature; said instantaneous sensing being accomplished at a rate equal to a least once during each time interval corresponding to said predetermined time interval. 